Question

শস্যাবর্তনের প্রধান সুবিধা লেখো​

Answer 1

Let the speed of the stream be x km/h.

Given, speed of water =3 km/h

Therefore, downstream speed =(x+3) km/h

and upstream speed =(x−3) km/h

Again, time taken in downstream and upstream is 15 hours and 20 hours respectively.

Now, distance downstream = distance upstream

⇒15(x+3)=20(x−3)

⇒15x+45=20x−60

⇒15x−20x=−60−45

⇒−5x=−105 or x=21 km/h

Therefore, downstream speed =21+3=24 km/h

So, distance between the two towns = Downstream speed × Time taken in downstream

=24×15=360 km